Thanks for your vote of confidence. While I respect that request and may in fact incorporate it, it is probably best left to other analytics. The profit you are seeing is composed of the selling price, minus any discount (currently a fudge factor until Shopify provides real discount amount info per item), minus the cost. Simple. Accurate and useful, especially at tax time when reporting profit is important.
I made it handle cancelled orders, and refunds too, so that is something, on top of internationalization.
Taxes, shipping, fees, are all clearly gross figures that contribute overhead to an order (and hence the products), but do not actually determine the profit per product. They affect more the profit per order. I will provide that once things shake down a little more if I can.
Anyway, the App will almost certainly improve as merchants speak up and email in their requests. Any and all good ones will be dealt with.
Thanks!